The present invention is generally directed to encapsulated toners and developers, and processes thereof, including for example a process for the preparation of custom and highlight colored toners. More specifically, the present invention in one embodiment is directed to a process for obtaining custom and highlight color toners by blending two or more encapsulated toners encompassed within a primary set of color encapsulated toners, and wherein the primary color encapsulated toners can be prepared by providing a polymeric core material containing a different primary pigment colorant and encapsulating the pigment colorant within each toner with a polymeric shell. In another embodiment, the present invention relates to processes for obtaining custom color toners comprised of a mixture of at least two passivated encapsulated toner compositions comprised, for example, of a core comprised of a polymer binder and colorants, including pigments, dyes, or mixtures thereof, and a polymeric shell thereover prepared, for example, by interfacial polymerization, and wherein the pigment, dye, or mixture in the encapsulated toners are comprised of different or dissimilar components, for example the first encapsulated toner may contain a cyan pigment, and the second encapsulated toner may contain a magenta pigment enabling a blue toner when the aforementioned toners are blended. Another embodiment of the present invention relates to processes for colored passivated toners comprised of a mixture of at least two encapsulated toners, wherein the core contains pigments such as cyan, magenta, yellow, red, blue, green, brown, black, white or mixtures thereof, and wherein the pigments in each toner are comprised of a different component, for example with two encapsulated toners the first pigment, which is passivated can be comprised of a cyan component, and the second pigment, which is passivated, can be comprised of a yellow pigment to enable a custom green encapsulated toner subsequent to mixing. Similarly, a mixture of a cyan encapsulated toner and a magenta encapsulated toner will enable a bluish encapsulated toner; and a mixture of a magenta and yellow encapsulated toner will enable a yellow encapsulated toner. In another embodiment of the present invention, there are provided processes for custom colored toners comprised of a first encapsulated toner and a second encapsulated toner, and wherein the aforementioned toners may possess the same or similar triboelectric characteristics and the same or similar admix properties, that is the toners are passivated in that, for example, the core pigments do not adversely affect the triboelectric characteristics thereof, and the tribo charge of the toners is independent of the core pigments selected. Toners with similar triboelectric and admix characteristics are of value in that, for example, the xerographic properties of only one color toner needs optimization instead of the usual 4 to 7 (for example, black, cyan, magenta, yellow, red, blue, brown, and the like); the toners can be selected for known highlight, trilevel imaging processes, and custom color processes; enabling color image stability in electrophotographic, especially xerographic, imaging apparatuses employing custom color processes, greatly expanding the number of custom color toners that can be prepared.
Several other advantages are associated with the present invention, including for the product desirable heat fusibility, triboelectric passivation of the components, especially the pigment components present in the core thereby avoiding or minimizing the electrical, especially the triboelectrical, degradation properties of the resulting toner caused by the pigment particles; narrow size distribution of the particles (GSD) of, for example, from 1.3 to about 1.7; stable shell characteristics; blocking temperatures, for example in an embodiment of the present invention blocking temperatures for the heat fusible toners, especially with polyurea shells, of greater than 80.degree. C.; avoidance or minimization of particle agglomeration and coalescence, especially at elevated core polymerization temperatures; excellent melt flow properties, for example, from about 10.degree. to about 50.degree. C. lower than a toner comprised of styrene n-butylmethacrylate, 88 weight percent, 10 weight percent of carbon black, and 2 weight percent of cetyl pyridinium chloride as a charge enhancing additive, and the like.
Toners suitable for use in electrophotographic apparatuses, including printers, may include therein a wide variety of colors, such as black, red, green, blue, brown, yellow, purple, silver and gold. When it is desired to highlight certain features of a document, one or more colored toners are typically used in conjunction with a black toner to provide an image in two or more colors. Full color images can also be generated by developing images with cyan, magenta, yellow and, optionally, black toners. Generally, it is advantageous for such toners to exhibit low melting temperatures to enable low energy fusing of the developed images to substrates at lower temperatures and lower pressures of 50 to 400 psi versus 4,000 psi for many prior art cold pressure fixable applications. It is also often advantageous for such toners to possess mean particle diameters of from about 2 microns to about 30 microns and preferably from about 2 microns to about 15 microns to enable images of high resolution, low image noise and high color fidelity. Further, it is generally desirable for these small diameter toners to possess narrow size distributions, preferably with a GSD (Geometric Standard Deviation) of 1.3 or less, to avoid difficulties in the electrophotographic development and transfer associated with oversize toner particles and extremely fine toner particles. These and other advantages can be achieved with the encapsulated toners and processes of the present invention in embodiments thereof.
The toner compositions of the present invention can be selected for a variety of known imaging and printing processes including electrophotographic processes. Specifically, the toner compositions of the present invention can be selected for xerographic imaging and printing processes including color processes, such as two component development systems and single component development systems, including both magnetic and nonmagnetic; and ionographic processes wherein dielectric receivers such as silicon carbide are utilized, reference U.S. Pat. No. 4,885,220, the disclosure of which is totally incorporated herein by reference.
With regard to embodiments of the present invention reference to the following is mentioned:
Triboelectric Passivation: When the xerographic properties such as triboelectric charge (tribo), admix, developer stability, humidity sensitivity, and the like of the highlight color and black toners are substantially equivalent, the toners can be considered triboelectrically passivated. One primary main advantage of a blended mixture of two passivated encapsulated toners is their interchangeability.
Highlight Color: A highlight color toner can be a single toner, of a single color of a usually saturated hue, which is employed with a second color toner, most commonly black toner. Such color toners may be imaged on documents with twin engine xerographic copiers or printers, where each engine comprises a separate charging, exposure, development, transfer, and cleaning step, one for each color toner, or with single engine xerographic copiers or printers which utilize two separate development stations, one for each color, and where the paper or transparency, or other throughput substrate makes either one or two cycles. An example of a single engine printing/copying device with only one cycle can be referred to as known trilevel xerography. Applications of highlight color include, for example, emphasizing important information, headlining titles in documents, slides, overhead transparencies, figures and the like. The image color density of a highlight color is controlled by the developed toner mass per unit area, for example the higher the toner mass per unit area, the darker the color. Typical highlight colors are common colors desired by many different types of customers, such as red, blue, brown, green, and the like.
Functional Color Toners: Highlight colors are not necessarily limited to black plus one color, but may also include black plus two colors or black plus 3 or more highlight colors. Black plus several colors, usually accomplished with multiple xerographic engines, can also be referred to as functional color, and might be employed, for example, in cartoon pictures, instruction manuals, utility bills, and the like. Functional colors are not usually mixed in the image, and are usually saturated.
Pictorial Color: Pictorial color refers to black plus 3 subtractive primary colors (cyan, magenta, and yellow), where the color toners are applied in successive layers, with continuous, or near continuous density, or developed toner mass to span as wide a color gamut as possible.
Custom Color Toner: A custom color toner is a very specific highlight color toner. Often toners with these colors are used for corporate logos and letterhead, or government flags, or official document seals, where the color coordinates are specified. Examples of custom colors are Xerox Corporation.RTM. Blue, IBM.RTM. Blue, Blue Cross.RTM. Blue, and the like. Other custom colors might include gold, silver, fluorescent colors, and the like.
Security Toners: Security toners are specific custom color toners created with either special ingredients which can be detected to authenticate documents (for example, infrared absorbing or fluorescing or radioactive or magnetic components), or special ingredients which prevent copying (for example, fluorescent materials which emit sufficient light when illuminated in typical copiers to discharge the photorecptor and blank out the encoded information). Like other custom color toners, these materials might be very specific to the end user, and might vary from customer to customer, or from application to application.
Known color toners fall into two different broad categories, conventional and encapsulated. Conventional color toners can be comprised of pigmented or dyed resin particles, while encapsulated toners are comprised of a pigmented or dyed resin core, and a protective shell overcoat. The conventional toners are most commonly prepared by an extended and involved process of compounding the pigment and optional additives with the resin, jetting of this material into toner sized particles, and classification of the toner. Since the cleaning of the blenders, extruders, and jetting mills between different color batches is labor intensive and expensive, this process may best be suited to the manufacture of medium to very large quantities of toner in batches larger than 1,000 kilograms, for example. Therefore, it is likely that this process is only economically feasible for those colors for which there is an aggregate demand of greater than several thousand kilograms of toner per year. Such conventional color toners are usually characterized by triboelectric and admix properties which vary from one color to another because of the well known and often very large effect of the pigment on the electroscopic properties. As a consequence of these variations in triboelectric properties from one color toner to another, each color toner usually requires an exhaustive research and development effort to obtain desirable triboelectric characteristics compatible with other colors in the set. Normally such research and development efforts for a pictorial color set (black plus cyan, magenta, and yellow) can consume four times as much time as the research and development optimization of a single black toner. Thus, the known conventional toner manufacturing approach is economically feasible for popular highlight colors, such as red, green, brown and blue. However, these processes can become prohibitively expensive for most custom colors. To offset the high cost of small batches of custom color toners, moderately large batches would have to be formulated and substantial inventories of different colored toner material maintained. These and other disadvantages are avoided or minimized with the toners and processes of the present invention.
The blending of conventional toners is known, reference for example U.S. Pat. Nos. 4,395,471 and 4,312,932. However, the extremely high research and development cost for optimization of the xerographic properties of blended conventional toners is still present, and inhibits application to custom color in the same way as unblended conventional toners.
An advantage of encapsulated toners, reference U.S. Pat. No. 4,937,167 and copending patent application U.S. Ser. No. 516,864, the disclosures of which are totally incorporated herein by reference, are that once the optimized xerographic and electroscopic properties of one color toner are obtained, the same properties are evident for the other colors. This dramatically shortens the research and development time to optimize a set of colored toners, for example, to perhaps 1.5 times as long for the pictorial four color set (cyan, magenta, yellow and black) compared to a single black toner. Therefore, the final cost of the color toners can be lower. Furthermore, it is much easier to introduce new colors using passivated encapsulated toners than using conventional melt blended and jetted toners because the new encapsulated toner will have the same tribo properties as the others in the set, while the new conventional toner will have different tribo properties, and can require another long and involved reserach and development cycle to optimize its electroscopic properties.
A number of encapsulated toners have disadvantages with regard to low volume highlight color processes, especially custom color toners, since for example (a) low volume production of, for example, only several kilograms is prohibitively expensive because the labor cost and complex reactor and overhead cost component of the synthesis is relatively large and the labor cost is independent of the batch size; (b) making custom colors by, for example, blending two or more cyan, magenta, yellow or other pigments in the toner formulation may give rise to unexpected effects, including (i) some variation in the particle size due to core viscosity differences, (ii) specific and undesirable interactions of new pigments with shell monomer components, (iii) specific and undesirable interactions between the mixed pigments which might lead to pigment agglomeration, a poor pigment dispersion, and poor color quality, (iv) obtaining a color unlike the target color, and other problems leading to unacceptable material or the like. These and other disadvantages can be avoided or minimized with the toners and processes of the present invention wherein, for example, there is accomplished the blending of passivated encapsulated color toners.
In a patentability search report, the following U.S. patents were recited, the disclosures of each of these patents being totally incorporated herein by reference, U.S. Pat. No. 4,937,167 which discloses the preparation of two encapsulated toner compositions of different colors and with similar triboelectric charging characteristics by a polymerization method and wherein for the first toner there is selected a pigment with a different color than the pigment for the second toner; U.S. Pat. Nos. 3,830,750; 3,893,932; 4,656,111 and as collateral interest U.S. Pat. Nos. 3,870,644; 4,066,563 and 4,070,296.
In one aspect, the present invention relates to the preparation of blendable passivated color toners, referred to as the primary set, which primary set could be economically manufactured in large volume batches, for example, of greater than 2,000 kilograms. Typical primary sets would include, as a minimum, one cyan toner, one magenta toner, and one yellow toner. Optional toners which could be included in a primary set are black, white, unpigmented, fluorescent, gold, silver, IR absorbing, metallic, and the like, which permit the possibility of added desirable effects to a variety of other color toners when blended with other toners in the primary set. One primary embodiment of the invention relates to the preparation of highlight color toners such as red, blue, green, brown, orange, and the like by blending two or more encapsulated toners from the primary set. For example, a variety of shades of red encapsulated toners can be generated by blending magenta and yellow primary toners in a variety of ratios, for example, from about 60 parts of a yellow encapsulated toner blended with about 40 parts of a magenta encapsulated to about 10 parts of yellow blended with 90 parts of magenta, with the optional addition of white, unpigmented, fluorescent or gold primary color toners for special effects. In another embodiment, a variety of shades of blue custom color toners, for example, for the logos of different companies can be obtained by blending magenta and cyan primary toners in a variety of ratios, for example, from about 25 parts of cyan blended with 75 parts of magenta to about 90 parts of cyan blended with 10 parts of magenta with optional addition of white, unpigmented, or black or fluorescent primary toners, for example in amounts of from about 1 part to about 200 parts by weight.
One advantage of blending passivated encapsulated toners from the primary set is that if the color of the blended toner is not correct, further addition of one or other original primary toner, or of a third primary toner to the original blend can be employed to achieve the target color properties without wastage of the first blended material, whereas prior art direct synthesis of a single color toner, which was off-specification, would be unusable, and the toner would likely have to be discarded. Another specific advantage of the present invention is that there are substantially no variations in particle size caused during synthesis by pigment variation because the primary set toners to be blended can be prepared in advance. Furthermore, since the number of primary toners in the set is relatively small, fewer synthetic optimizations are required than would be the situation with the prior art. Also, another advantage of the present invention is that the blended toner pigments cannot agglomerate with one another, as they might within a single toner, because they are isolated in separate toner particles in the primary set of toners. Other examples of advantages of the the present invention include small batches of highlight or custom color toners can be blended from the primary set at very low cost. This would permit a more rapid response to customer needs as they arose.
Other advantages include the primary toner synthesis steps could be perfomed on an economically large scale to provide, for example, blendable cyan, magenta, and yellow toners, such materials being of lower cost as they can be manufactured on a large scale; no need for xerographic optimization of each blended toner as it was prepared since the encapsulation process provides triboelectrically passivated toners, the blended color toners have the same triboelectric properties as any other color toner made from the same primary set of blendable toners, and the same triboelectric properties as the primary set itself. The blended encapsulated toners provided could thus be immediate "drop in" replacements for printers or xerographic imaging apparatus without the need for costly qualification processes to determine their performance.
A further advantage of the present invention resides in the range and number of economically feasible highlight or custom color toners available to customers compared to the limited range and number of economically feasible highlight or custom color toners presently available. With the present invention, an economically feasible highlight or custom color toner could be of any color in the range available from the blendable primary toners, and not limited to toners where there was an aggregate demand of several thousand kilograms. At the same time as the range and number of economically feasible color toners is expanded by the present invention, expensive toner inventory costs are minimized because only the primary blendable toners need to be stored. Toners can be blended as required for shipment. This reduces the cost to the manufacturer and to the customer, and expands the use and applicability of highlight and custom color toners.
Yet another specific advantage of the present invention is the simplification of the research and development optimization of security toners. For example, if an IR absorbing primary toner were blended with a cyan primary toner to provide an IR absorbing blended cyan custom color security toner, and this toner was imaged on documents owned by a certain customer, the origin of the documents generated could be deduced at later times from the IR absorbing characteristics of the cyan printed areas.
A further advantage of the present invention is that the same primary set of blendable toners can be maintained for pictorial color toners as well as for highlight and custom color toners. Thus, a basic inventory of only a few primary toners, for example a primary set of three color toners (cyan, magenta, and yellow) plus black, could be used for pictorial color printing and copying as well as to prepare a highlight set of blended red, blue, brown, and green toners, and to prepare blended custom color toners for a number of potential customers, and wherein optimization of only one set of triboelectric properties is needed. By contrast, using conventional toners, this would require separate preparation, and xerographic optimization of storage and maintenance of, for example, 16 toners if half of them were custom color toners.
Likewise, the addition of optional white, unpigmented, fluorescent, metallic, silver, gold or metallic toners to the primary toner set could further increase the range of potential highlight and custom colors available from blending encapsulated passivated toners.
Yet another advantage of the present invention is that encapsulation of conductive metals will yield insulating gold, silver and bronze colored toners needed for two component or single component development, whereas conventional toners with these pigments would usually be too conductive to charge or transfer properly.
A further advantage of the present invention is that encapsulated toners can be readily synthesized in small particle sizes, as small as 2 microns. This feature enables high copy quality at little or no additional cost. In contrast, conventional toners made by melt blending, extrusion, micronization and classification are characterized by rapidly increasing cost as the particle size d.sub.50 is reduced significantly below 10 microns.
In yet another advantage of the present invention, magnetic ink character recognition (MICR) toner can be considered a custom color toner for use in the check printing or security printing business. The MICR toner could be added to the primary set and be employed as a custom highlight color on black or color documents, thus avoiding the extra expense of printing the entire document with the (usually) more expensive magnetic toner, and greatly expanding the range of copiers and printers with MICR capability.
The process of the present invention is also advantageous because all toners in a primary and blended color set can possess the same tribo and admix properties (passivation). This feature can (a) dramatically shorten color copier and printer research and development cycles since only one set of tribo and admix properties needs optimization, rather than 4 to 7; (b) enable any highlight or custom color to be use; (c) result in much more reliable color stability in copying and printing machines employing blended custom color toners; and (d) greatly increase the range of custom color toners which can be prepared from a limited inventory.
The encapsulated toner compositions selected for the present invention can also utilize a shell with substantially improved mechanical properties, and which shell does not rupture prematurely causing the core component comprised, for example, of a polymer and pigment to become exposed, and contaminating the image development subsystem surfaces or forming undesirable agglomerates. The toner compositions of the present invention can be selected for a variety of known reprographic imaging processes including electrophotographic, especially xerographic processes. Another application of the toner compositions of the present invention resides in its use for two component development systems wherein, for example, the image toning and transfer are accomplished electrostatically, and the fixing of the transferred image is achieved by application of pressure with or without the assistance of thermal energy.
The toner compositions of the present invention can, in embodiments, be prepared by a shell forming interfacial polycondensation, followed by an in situ core polymer binder forming free radical polymerization of an addition monomer or monomers initiated by thermal decomposition of a free radical initiator. In one embodiment of the present invention, the toners can be prepared by the simple and economical chemical microencapsulation method involving an interfacial polycondensation and a free radical polymerization, and wherein there are selected, for example, acrylates, methacrylates or styryl derivatives as core monomers, pigments or dyes as colorants, and polyisocyanates and amines as shell precursors to provide encapsulated toners with a polymeric shell. Further, in another process aspect of the present invention the encapsulated toners can be prepared in the absence of flammable organic solvents, thus eliminating explosion hazards associated therewith; and furthermore, these processes do not require the expensive and hazardous solvent separation and recovery steps. Moreover, with the process of the present invention there can be obtained in some instances improved yields of toner products since, for example, the extraneous solvent component can be replaced by liquid shell and core precursors.
In a patentability search report for encapsulated toners, there were recited as prior art the following U.S. patents: U.S. Pat. No. 4,830,144 directed to encapsulated pressure fixable toners with an electroconductive powder coating, reference the Abstract of the Disclosure, and the disclosure beginning in column 3, around line 48. Examples of shell components are illustrated in column 4, beginning at around line 33, and note specifically the disclosure in column 4, beginning at line 47, wherein shells are produced by the polycondensation reaction between polyisocyanates and one or more of the counterpart compounds such as polyo, polythio, polyamine, water, and perpazine can be selected; the preparation of the encapsulated toner of this patent is illustrated in column 7, beginning at line 6; examples of colorants included in the core, which colorants may comprise dyes, pigments, and the like, are illustrated beginning in column 8; surface active agents selected for the encapsulated toner of the '144 patent are illustrated in column 11, while examples of the electroconductive material include components such as antimony, halogen, and the like, reference Claim 1, for example; U.S. Pat. No. 4,721,651 directed to microcapsules of the type selected for pressure sensitive carbonless copy papers with walls formed of an aliphatic diisocyanate and a diamine and containing, for example, a solvent mixture with a dye precursor dissolved therein, note for example the disclosure beginning in column 2, the working Examples, and Claim 1; a similar teaching is present in U.S. Pat. Nos. 4,622,267; 4,738,898 directed to microencapsulation by interfacial polyaddition of, for example, an aliphatic diisocyanate and an isocyanurate triamer, and wherein the aforementioned components can be interfacially reacted with a polyamine; the selection of carboxy methylcellulose, sodium salt, is illustrated in the working Examples, reference working Example 1, column 5, beginning at line 26; further, note the disclosure in column 3, beginning at line 46, wherein it is indicated that it is envisioned, for example, to encapsulate plant protection agents such as herbicides, fungicides, or insecticides, which makes then less hazardous to handle, and it is also intended to encapsulate the pharmaceutical products, food products, flavors, perfumes, colorants, paints, or catalysts, reference the disclosure in column 3, beginning at line 46; U.S. Pat. No. 4,766,051, the disclosure of which is totally incorporated herein by reference, directed to colored encapsulated toner compositions, and more specifically, cold pressure fixable colored toner compositions comprised of a core containing a polymer in which is dispersed pigment particles selected from the group consisting of cyan, magenta, red, yellow pigments, and mixtures thereof, and magnetites encapsulated within a polymeric shell formulated by an interfacial polymerization, note specifically, for example, the disclosure in column 3, beginning at line 35, and continuing on to column 15, and note that polyvinyl alcohol may be selected, and more specifically, for example, the organic phase can be dispersed by a polytron in an aqueous phase containing polyvinyl alcohol to obtain toner particles, see column 6, beginning at line 28, and note specifically the working Examples, especially working Example 11; and U.S. Pat. No. 4,193,889 directed to microencapsulation with modified polyisocyanates, and more specifically to microcapsules and a process thereof, the walls of which consist of polycondensates of a film forming aliphatic polyisocyanate containing at least one biurett group or polyaddition products thereof with a chain extending agent, reference the Abstract of the Disclosure; and note the disclosure in columns 2,3 and 4.
In a copending application directed to encapsulated toner, there were mentioned in a patentability search report the following U.S. patents: U.S. Pat. No. 4,727,101, the disclosure of which is totally incorporated herein by reference, which illustrates a free radical polymerization of a toner shell at elevated temperatures and more specifically is directed to the preparation of encapsulated toner compositions, which comprises mixing in the absence of a solvent a core monomer, initiator, pigment particles, a first shell monomer, stabilizer, and water, and thereafter adding a second shell monomer to enable an interfacial polymerization interaction, and subsequently affecting the free radical polymerization of the core monomer, reference the Abstract of the Disclosure for example; U.S. Pat. No. 4,777,104 the disclosure of which is totally incorporated herein by reference, which relates to processes for the formation of electrophotographic toners of certain desired sizes by radical polymerization, reference for example column 3, lines 26 to 41, and also note the disclosure in column 6 with respect to colorants, beginning at line 29; U.S. Pat. No. 4,524,199, the disclosure of which is totally incorporated herein by reference, which relates to stable polymeric dispersions, which dispersion comprises, for example, a polar dispersion medium having dispersed therein particles comprising a thermoplastic resin core having irreversibly anchored thereto a nonionic amphipathic steric stabilizer comprising a graft copolymer, reference for example column 2, beginning at line 45, and note column 4, beginning at line 57, and continuing on to column 5; U.S. Pat. No. 4,533,617 the disclosure of which is totally incorporated herein by reference, directed to heat fixable developers with a capsule structure containing a binder resin of a certain glass transition temperature and a colorant coated with a vinyl type polymer, reference for example the Abstract of the Disclosure, and note columns 4 through 10; U.S. Pat. No. 4,725,522 directed to processes for cold pressure fixable encapsulated toner compositions, particularly processes thereof wherein a water phase containing a stabilizing material is selected and hydrolysis is accomplished by heating and there is utilized interfacial polymerization to form the shell, reference for example the Abstract of the Disclosure, and also note columns 4 to 8, the disclosure of the aforementioned patent being totally incorporated herein by reference; U.S. Pat. No. 3,876,610 relating to the preparation of electrostatic toner materials with a size between 1 to 10 microns and containing a polymeric shell comprising a copolymer with a glass transition temperature of at least 40.degree. C., see the Abstract of the Disclosure for example, the disclosure of the aforementioned patent being totally incorporated herein by reference; and U.S. Pat. No. 4,762,752 which discloses addition compounds suitable as dispersing agents, reference the Abstract of the Disclosure, for example the disclosure of the aforementioned patent being totally incorporated herein by reference.
Additionally, there is illustrated in U.S. Pat. No. 4,565,764 a pressure fixable microcapsule toner having a colored core material coated successively with a first resin wall and a second resin wall. The first resin wall has affinity to both the core material and the second resin wall. This patent teaches that the first resin wall may be of a material that becomes charged to a polarity opposite to that of the second resin wall and the core material.
Also, U.S. Pat. No. 4,520,091, the disclosure of which is toally incorporated herein by reference, illustrates a pressure fixable encapsulated electrostatographic toner material. The core comprises a colorant, a polymer, a solvent capable of dissolving the polymer or causing the polymer to swell, and an organic liquid incapable of dissolving the polymer or causing the polymer to swell, while the shell may consist of a polyamide resin. Preparation of the toner material is completed by interfacial polymerization.
Another patent, U.S. Pat. No. 4,708,924, the disclosure of which is totally incorporated herein by reference, describes a pressure fixable microcapsule type toner composed of a core material and an outer wall covering over the core material. The core material contains at least a combination of a substance having a glass transition point within the range of -90.degree. C. to 5.degree. C. with a substance having a softening point within the range of 25.degree. C. to 180.degree. C. This toner composition may comprise substances, such as polystyrene and poly(n-butylmethacrylate), and their copolymers.
Further, U.S. Pat. No. 4,254,201, the disclosure of which is totally incorporated herein by reference, illustrates a pressure sensitive adhesive toner consisting essentially of porous aggregates. Each aggregate consists essentially of a cluster of a multiplicity of individual granules of pressure sensitive adhesive substance, each granule being encapsulated by a coating film of a film-forming material. Particles of an inorganic or organic pigment and/or a magnetic substance are contained within the aggregate in the interstices between the granules and deposited on the surfaces of the encapsulated granules. The adhesive substance is selected from a copolymer of at least one monomer and as many as three other monomers.
In addition, U.S. Pat. No. 4,702,988, the disclosure of which is totally incorporated herein by reference, illustrates a process for the preparation of encapsulated toner. A monomer composition and a colorant are dispersed in a liquid dispersion medium in the presence of a solid fine powdery dispersion stabilizer. The liquid is pressurized and then ejected into a low pressure section to form particles of monomer composition. These particles are then subjected to suspension polymerization to produce toner particles.
In U.S. Pat. No. 4,727,011 there is disclosed a process for preparing encapsulated toner compositions, which comprises mixing, in the absence of a solvent, a core monomer, an initiator, pigment particles, a first shell monomer, stabilizer, and water; thereafter adding a second shell monomer, thereby enabling an interfacial polymerization reaction between the first and second shell monomers; and subsequently effecting a free radical polymerization of the core monomer. The disclosure of this patent is totally incorporated herein by reference.
Also, U.S. Pat. No. 4,855,209, the disclosure of which is totally incorporated herein by reference, discloses an encapsulated toner composition with a melting temperature of from about 65.degree. C. to about 140.degree. C. which comprises a core containing a polymer selected from the group consisting of polyethylene succinate, polyhalogenated olefins, poly(.alpha.-alkylstyrenes), rosin modified maleic resins, aliphatic hydrocarbon resins, poly(.epsilon.-caprolactones), and mixtures thereof; and pigment particles, where the core is encapsulated in a shell prepared by interfacial polymerization reactions.
There are disclosed in U.S. Pat. No. 4,307,169, the disclosure of which is totally incorporated herein by reference, microcapsular electrostatic marking particles containing a pressure fixable core, and an encapsulating substance comprised of a pressure rupturable shell, wherein the shell is formed by an interfacial polymerization. One shell prepared in accordance with the teachings of this patent is a polyamide obtained by interfacial polymerization. Furthermore, there is disclosed in U.S. Pat. No. 4,407,922, the disclosure of which is totally incorporated herein by reference, pressure sensitive toner compositions comprised of a blend of two immiscible polymers selected from the group consisting of certain polymers as a hard component, and polyoctyldecylvinylether-co-maleic anhydride as a soft component. Interfacial polymerization processes are also selected for the preparation of the toners of this patent. Also, there are disclosed in the prior art encapsulated toner compositions containing costly pigments and dyes, reference for example the color photocapsule toners of U.S. Pat. Nos. 4,399,209; 4,482,624; 4,483,912 and 4,397,483.
Further, U.S. Pat. No. 4,851,318 discloses an improved process for preparing encapsulated toner compositions which comprises mixing core monomers, an initiator, pigment particles, and oil soluble shell monomers, homogenizing the mixture into an aqueous surfactant solution to result in an oil-in-water suspension enabling an interfacial polymerization reaction between the oil soluble and the water soluble shell monomers, subsequently adding a low molecular weight polyethylene oxide surfactant protective colloid, and thereafter effecting free radical polymerization of the core monomers by heating. The disclosure of this U.S. Pat. No. 4,851,318 is totally incorporated herein by reference.
Moreover, illustrated in U.S. Pat. No. 4,758,506, the disclosure of which is totally incorporated herein by reference, are single component cold pressure fixable toner compositions, wherein the shell selected can be prepared by an interfacial polymerization process.
There is illustrated in U.S. Pat. No. 4,937,167, the disclosure of which is totally incorporated herein by reference, a process for controlling the electrical characteristics of colored toner particles.
There is also illustrated in U.S. Pat. No. 5,035,970, the disclosure of which is totally incorporated herein by reference, an encapsulated toner composition comprised of a core comprised of pigments or dyes, and a polymer; and wherein the core is encapsulated in a polyester shell with functional groups thereon, and derived from diacid halide polyesters.
U.S. Pat. No. 5,037,716, the disclosure of which is totally incorporated herein by reference, illustrates encapsulated toners with a Daxad dispersant. To stabilize heat fusible particles at elevated temperatures, the addition of a Daxad dispersant is used to prevent particle agglomeration and coalescence. The encapsulated toner composition comprises a core comprised of a performer polymer and/or monomer or monomers, a free radical initiator, pigment or dye particles where the core is dispersed in an emulsifier solution, and subsequently encapsulated in a polymeric shell and wherein the toner is stabilized by Daxad dispersants during core polymerization, where the dispersant is a naphthalene sulfonate formaldehyde condensate material. With this process the emulsifier was not able to lower the GSD below 1.5 without classification. The incorporation of Daxad can be added after the particle generation step.
Free radical polymerization is a well known art, and can be generalized as bulk, solution, emulsion or suspension polymerization. These polymerizations are commonly selected for the preparation of certain polymers. The kinetics and mechanisms for free radical polymerization of monomer(s) is also well known. In these processes, the control of polymer properties such as molecular weight and molecular weight dispersity can be effected by initiator, species concentrations, temperatures, and temperature profiles. Similarly, conversion of monomer is effected by the above variables.
Interfacial polymerization processes are described in British Patent Publication 1,371,179, the disclosure of which is totally incorporated herein by reference, which publication illustrates a method of microencapsulation based on in situ interfacial condensation polymerization. More specifically, this publication discloses a process which permits the encapsulation of organic pesticides by the hydrolysis of polymethylene polyphenylisocyanate or toluene diisocyanate monomers. Also, the shell-forming reaction disclosed in the aforementioned publication is initiated by heating the mixture to an elevated temperature at which point the isocyanate monomers are hydrolyzed at the interface to form amines, which then react with unhydrolyzed isocyanate monomers to enable the formation of a polyurea microcapsule wall.
Furthermore, other prior art, primarily of background interest, includes U.S. Pat. Nos. 4,254,201; 4,465,755 and Japanese Patent Publication 58-100857. The Japanese publication discloses a capsule toner with high mechanical strength, which is comprised of a core material including a display recording material, a binder, and an outer shell, which outer shell is preferably comprised of a polyurea resin. In the '201 patent there are disclosed encapsulated electrostatographic toners wherein the shell material comprises at least one resin selected from polyurethane resins, a polyurea resin, or a polyamide resin. In addition, the '755 patent discloses a pressure fixable toner comprising encapsulated particles containing a curing agent, and wherein the shell is comprised of a polyurethane, a polyurea, or a polythiourethane. Moreover, in the '201 patent there are illustrated pressure sensitive adhesive toners comprised of clustered encapsulated porous particles, which toners are prepared by spray drying an aqueous dispersion of the granules containing an encapsulated material.
Also, there are illustrated in U.S. Pat. No. 4,280,833 encapsulated materials prepared by interfacial polymerization in aqueous herbicidal compositions. More specifically, as indicated in column 4, beginning at line 9, there is disclosed a process for encapsulating the water immiscible material within the shell of the polyurea, a water immiscible organic phase which consists of a water immiscible material, that is the material to be encapsulated, and polymethyl polyphenyl isocyanate is added to the aqueous phase with agitation to form a dispersion of small droplets of the water immiscible phase within the aqueous phase; and thereafter, a polyfunctional amine is added with continuous agitation to the organic aqueous dispersion, reference column 4, lines 15 to 27. Also, note column 5, line 50, wherein the amine selected can be diethylene triamine, and the core material can be any liquid, oil, meltable solid or solvent soluble material, reference column 4, line 30. A similar teaching is present in U.S. Pat. No. 4,417,916.
In U.S. Pat. No. 4,599,271, the disclosure of which is totally incorporated herein by reference, there are illustrated microcapsules obtained by mixing organic materials in water emulsions at reaction parameters that permit the emulsified organic droplets of each emulsion to collide with one another, reference the disclosure in column 4, lines 5 to 35. Examples of polymeric shells are illustrated, for example, in column 5, beginning at line 40, and include isocyanate compounds such as toluene diisocyanate, and polymethylene polyphenyl isocyanates. Further, in column 6, at line 54, it is indicated that the microcapsules disclosed are not limited to use on carbonless copying systems; rather, the film material could comprise other components including xerographic toners, see column 6, line 54.
Other prior art includes U.S. Pat. No. 4,520,091, the disclosure of which is totally incorporated herein by reference, which illustrates an encapsulated toner material wherein the shell can be formed by reacting a compound having an isocyanate with a polyamine, reference column 4, lines 30 to 61, and column 5, line 19; and U.S. Pat. No. 3,900,669 illustrating a pressure sensitive recording sheet comprising a microcapsule with polyurea walls, and wherein polymethylene polyphenyl isocyanate can be reacted with a polyamine to produce the shell, see column 4, line 34.
Illustrated in U.S. Pat. No. 4,758,506, the disclosure of which is totally incorporated herein by reference, are single component cold pressure fixable toner compositions, wherein the shell selected can be prepared by an interfacial polymerization process.
In U.S. Pat. No. 5,043,240, the disclosure of which is totally incorporated herein by reference, there are illustrated encapsulated toners with a core comprised of a polymer binder, pigment or dye, and thereover a polymeric shell, which contains a soft and flexible component, permitting, for example, proper packing of shell materials resulting in the formation of a high density shell structure, which can effectively contain the core binder and prevent its loss through diffusion and leaching process. The soft and flexible component in one embodiment is comprised of a polyether function. Specifically, in one embodiment there is disclosed in the aforementioned patent encapsulated toners comprised of a core containing a polymer binder, pigment or dye particles, and thereover a shell preferably obtained by interfacial polymerization, which shell has incorporated therein a polyether structural moiety. Another specific embodiment of the patent is directed to encapsulated toners comprised of a core of polymer binder, pigment, dye or mixtures thereof, and a polymeric shell of a polyether-incorporated polymer, such as a poly(ether urea), a poly(ether amide), a poly(ether ester), a poly(ether urethane), mixtures thereof, and the like.
In U.S. Pat. No. 5,045,422, the disclosure of which is totally incorporated herein by reference, there are illustrated encapsulated toners with a core comprised of a polymer binder, pigment or dye, and thereover a hydroxylated polyurethane shell, and which shell has the ability to effectively contain the core binder and prevent its loss through diffusion and leaching process. Specifically, in one embodiment there is provided in accordance with the patent encapsulated toners comprised of a core containing a polymer binder, pigment or dye particles, and thereover a hydroxylated polyurethane shell derived from the polycondensation of a polyisocyanate and a water-soluble carbohydrate, such as a monosaccharide, a disaccharide or their derivatives, with the polycondensation being accomplished by the known interfacial polymerization methods. Another specific embodiment of the patent is directed to pressure fixable encapsulated toners comprised of a core of polymer binder, magnetic pigment, color pigment, dye or mixtures thereof, and a hydroxylated polyurethane shell, and coated thereover with a layer of conductive components such as carbon black.
Accordingly, there is a need for encapsulated toner compositions with many of the advantages illustrated herein. More specifically, there is a need for custom, and highlight color encapsulated toners wherein the pigments are passivated, and wherein the toners may contain shells that eliminate or minimize the loss of core components such as the binder resin. Also, there is a need for encapsulated toners wherein color images with excellent resolution and superior fix can be obtained.